I remember the last time I used dropbox on my laptop. I tried to open a random file outside my dropbox folder and I got the error message that I can not open it

I remember the last time I used dropbox on my laptop. I tried to open a random file outside my dropbox folder and I got the error message that I can not open it because it is used by dropbox at this moment. I deleted the desktop app at that moment. I am not an OS hacker but as a user I am pretty sure the desktop app should not access files outside my dropbox folder. The excuse of "testing some desktop features" is pretty lame. If you catch your housemaid sniffling your panties it is simply not an effing feature, even if your panties are clean and sexy! And this is not part of the mass surveillance...